TWI439024B - Cascade frequency converter and power unit with bypass module thereof - Google Patents

Description

Cascaded frequency converter, power unit and its bypass module

The invention relates to the technical field of frequency converters, and more particularly to a cascade type frequency converter, a power unit and a bypass module thereof.

With the rapid development of modern power electronics and microelectronics technology, high-power inverters are constantly being matured, especially in the case where the reliability of medium and high-voltage device applications is not too high and expensive. In recent years, people have passed low voltage. The cascading of power units makes this problem well solved, so the field and scope of cascaded frequency converter applications is becoming more and more extensive, which makes it possible to use energy (especially electrical energy) efficiently and reasonably.

In cascaded drives, the number of power units varies depending on the drive voltage level. For example, 6kV inverter, each phase usually has 5 or 6 power units connected in series, each power unit provides the same output voltage, a total of 15 or 18 power units, and 10kV inverter, the number of power units is up to 27, so many power units, once a power unit fails, if there is no reasonable treatment, the entire inverter will fail and cannot continue to operate, which will cause certain economic losses or enlarge the accident. The reliability of the frequency converter becomes lower due to the large number of power units.

The power unit bypass circuit can effectively solve this problem. Since the main circuit is turned on during the normal operation of the power unit, that is, the main circuit works normally, the entire inverter can work normally, so the BY PASS circuit of the power unit of the cascade type inverter is the main unit of a power unit. In the event of a circuit failure, a bypass device that bypasses (shorts) the main circuit of the faulty power unit in order not to cause the entire inverter system to shut down. In the prior art, in the cascade type inverter, each power unit has a bypass circuit. When the main circuit of a power unit fails and cannot output the voltage normally, in order not to cause the entire inverter to stop, it is necessary to utilize The bypass circuit of the faulty unit bypasses (short-circuits) the faulty part, that is, the corresponding bypass circuit is cut to work, so that the main circuit of the faulty power unit is bypassed, so that the entire frequency converter can continue to operate, ensuring no Economic or other losses due to inverter shutdown.

Chinese Patent Application No. 201010218945.2 discloses a unit bypass circuit of a unit cascade high-voltage frequency converter. When the power unit of the bypass circuit fails, it is necessary to manually close the mechanical operation knife gate, replace the faulty power unit, and then operate the mechanical operation knife switch. Disconnected, inefficient.

The prior art also discloses a technical solution using the mechanical mode of the contactor as the bypass circuit as shown in FIG. 1 , which is controlled by the auxiliary switch KM to be switched or disconnected. The bypass circuit has high reliability and is low in power inverter. There are advantages in the system, but in high-power inverter systems, due to the large size and high cost of the contactor, the system design is more complicated and the cost is higher.

In summary, the bypass circuit in the prior art cascaded frequency converter has the disadvantages of high cost, large volume, and the like, and needs further improvement.

The object of the present invention is to provide a cascaded frequency converter, a power unit and a bypass module thereof, which effectively solve the problems of high cost and large volume of the existing bypass circuit, and the circuit structure is simple, the conduction loss is low, and the reliability is reliable. High sex.

A cascaded inverter power unit bypass module for achieving the object of the present invention is used to bypass a main circuit module of the power unit, the main circuit module including a fuse, a rectifier, a bus capacitor, and an H inverse Transforming the bridge, two points are drawn from the H inverter bridge as a first output end and a second output end of the main circuit module, including a bypass circuit; the bypass circuit includes a first switching element, a second a switching element, a first diode and a second diode; the bypass circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a switching element, and the second bridge arm includes a diode; a point from the first leg of the bypass circuit as a first input of the bypass circuit, and a point from the second arm of the bypass circuit as a second input of the bypass circuit The first input end is electrically connected to the first output end of the main circuit module, and the second input end is electrically connected to the second output end of the main circuit module; when the main circuit module fails a switching element of the bypass circuit when the bypass circuit is cut A diode conduction to bypass the circuit module corresponding primary power unit.

The first switching element is a first insulated gate bipolar transistor, and the second switching element is a second insulated gate bipolar transistor.

The bypass circuit includes the first insulated gate bipolar transistor, the second insulated gate bipolar transistor, the first diode and the second diode; the first insulated gate bipolar transistor The emitter is electrically connected to the collector of the second insulated gate bipolar transistor, and the anode of the first diode and the cathode of the second diode are electrically connected, the first insulated gate bipolar transistor The collector is electrically connected to the cathode of the first diode, and the emitter of the second insulated gate bipolar transistor is electrically connected to the anode of the second diode; in the first insulated gate bipolar type a point between the transistor and the second insulated gate bipolar transistor leads a wire as a first input of the bypass circuit; a point between the first diode and the second diode leads a wire a second input terminal of the bypass circuit; the first diode and the first insulated gate bipolar transistor constitute a first branch, and the second diode and the second insulated gate bipolar transistor are formed a second branch; the first output end of the main circuit module is electrically connected to the side A second input of the first input of the circuit, a second output terminal of the main circuit module electrically connected to the bypass circuit.

Wherein, the current received by the first input end of the bypass circuit is negative, and the current received by the second input terminal is positive, the main circuit module of the power unit fails, and the bypass circuit is cut to work, then the bypass circuit The first diode and the first insulated gate bipolar transistor are turned on to bypass the main circuit module of the corresponding power unit, so that the entire cascaded frequency converter can continue to operate.

Wherein, the current received by the first input end of the bypass circuit is positive, and when the current received by the second input terminal is negative, the main circuit module of the power unit fails and the bypass circuit is cut to work, then the bypass circuit The second diode and the second insulated gate bipolar transistor are turned on to bypass the main circuit module of the corresponding power unit, so that the entire cascaded frequency converter can continue to operate.

The bypass circuit includes the first insulated gate bipolar transistor, the second insulated gate bipolar transistor, the first diode and the second diode; the first insulated gate bipolar transistor The collector is electrically connected to the emitter of the second insulated gate bipolar transistor, and the cathode of the first diode is electrically connected to the anode of the second diode, the first insulated gate bipolar transistor The emitter is electrically connected to the anode of the first diode, the collector of the second insulated gate bipolar transistor is electrically connected to the cathode of the second diode; and the first insulated gate bipolar type a point between the transistor and the second insulated gate bipolar transistor leads a wire as a first input of the bypass circuit; a point between the first diode and the second diode leads a wire a second input terminal of the bypass circuit; the first diode and the first insulated gate bipolar transistor constitute a first branch, and the second diode and the second insulated gate bipolar transistor are formed a second branch; the first output end of the main circuit module is electrically connected to the side A second input of the first input of the circuit, a second output terminal of the main circuit module electrically connected to the bypass circuit.

Wherein, the current received by the first input end of the bypass circuit is positive, and when the current received by the second input terminal is negative, the main circuit module of the power unit fails and the bypass circuit is cut to work, then the bypass circuit The first diode and the first insulated gate bipolar transistor are turned on to bypass the main circuit module of the corresponding power unit so that the entire cascaded frequency converter can continue to operate.

Wherein, the current received by the first input end of the bypass circuit is negative, and the current received by the second input terminal is positive, the main circuit module of the power unit fails, and the bypass circuit is cut to work, then the bypass circuit The second diode and the second insulated gate bipolar transistor are turned on to bypass the main circuit module of the corresponding power unit so that the entire cascaded frequency converter can continue to operate.

The bypass circuit includes the first insulated gate bipolar transistor, the second insulated gate bipolar transistor, the first diode and the second diode; the first insulated gate bipolar transistor The emitter is electrically connected to the anode of the first diode, and the emitter of the second insulated gate bipolar transistor is electrically connected to the anode of the second diode, the first insulated gate bipolar transistor The collector is electrically connected to the cathode of the second diode, the collector of the second insulated gate bipolar transistor is electrically connected to the cathode of the first diode; and the first insulated gate bipolar type a point between the transistor and the first diode leads a wire as a first input of the bypass circuit; a point between the second insulated gate bipolar transistor and the second diode leads a wire a second input terminal of the bypass circuit; the first diode and the second insulated gate bipolar transistor form a first branch, and the second diode and the first insulated gate bipolar transistor are formed a second branch; the first output end of the main circuit module is electrically connected to the side A second input of the first input of the circuit, a second output terminal of the main circuit module electrically connected to the bypass circuit.

Wherein, the current received by the first input end of the bypass circuit is positive, and when the current received by the second input terminal is negative, the main circuit module of the power unit fails and the bypass circuit is cut to work, then the bypass circuit The first diode and the second insulated gate bipolar transistor are turned on to bypass the main circuit module of the corresponding power unit so that the entire cascaded frequency converter can continue to operate.

Wherein, the current received by the first input end of the bypass circuit is negative, and the current received by the second input terminal is positive, the main circuit module of the power unit fails, and the bypass circuit is cut to work, then the bypass circuit The second diode and the first insulated gate bipolar transistor are turned on to bypass the main circuit module of the corresponding power unit so that the entire cascaded frequency converter can continue to operate.

The bypass circuit further includes an absorbing circuit, and the absorbing circuit includes an absorbing capacitor connected in parallel to both ends of the bypass circuit.

The absorbing circuit further includes a third protection resistor; the absorbing capacitor and the third protection resistor are connected in series and are connected in parallel to both ends of the bypass circuit.

The first protection resistor and the second protection resistor are electrically connected to one end of the first protection resistor, and the other end of the first protection resistor is electrically connected to one end of the bus capacitor. One end of the second protection resistor is electrically connected to the other end of the absorption capacitor, and the other end of the second protection resistor is electrically connected to the other end of the bus capacitor.

The bypass circuit further includes an RC branch and a bypass circuit state detecting unit; the RC branch includes a fourth resistor and a storage capacitor, and the fourth resistor and the storage capacitor are connected in series and then connected in parallel to the bypass circuit The two ends of the bypass circuit state detecting unit are connected in parallel with the RC branch to detect whether the bypass circuit operates.

The bypass control circuit is further electrically connected to the first switching element and the second switch for controlling conduction or disconnection of the first switching element and the second switching element.

The gates of the first insulated gate bipolar transistor and the second insulated gate bipolar transistor are connected to the bypass control circuit.

The invention also discloses a cascading type inverter power unit, comprising a main circuit module, a power unit control module and a bypass module; the main circuit module comprises a fuse, a rectifier, a bus capacitor, and an H inverter bridge, The H inverter bridge leads two points as two output ends of the main circuit module; the bypass module is a bypass module as described above; two input ends of the bypass circuit and the main circuit mode The two output terminals of the group are docked; the power unit control module is electrically connected to the main circuit module and the bypass module.

The power unit control module includes a control circuit and a fault detecting unit. The fault detecting unit is configured to detect whether the main circuit module is faulty. The control circuit is configured to send a fault detection signal when the fault detecting unit detects a fault.

The fault detecting unit includes a phase loss detecting circuit and/or a bridge arm fault detecting circuit; the phase loss detecting circuit is electrically connected to a three-phase input of an AC power source passing through the fuse, and is configured to detect that the main circuit module is in the Whether the AC input terminal is faulty; the bridge arm fault detection circuit is electrically connected to the H inverter bridge, and is used to detect whether the H inverter bridge is faulty.

The invention also discloses a cascade type frequency converter comprising a phase shifting transformer, a power unit and a three-phase load, the power unit comprising a main circuit module, a bypass module and a power unit control module; the main circuit module comprises a fuse , a rectifier, a busbar capacitor, an H-inverter bridge, two points are drawn from the H-inverter bridge as two output ends of the main circuit module; the bypass module is the first item of claim patent claim The bypass module of any one of the seventeenth; the two input ends of the bypass circuit are connected to the two output ends of the main circuit module; the power unit control module and the main circuit module and the The bypass module is electrically connected.

Wherein, the phase shifting transformer comprises at least one secondary winding.

The three-phase output of each secondary winding of the phase shifting transformer is respectively connected to the three-phase input end of the power unit.

The power unit control module includes a control circuit and a fault detecting unit. The fault detecting unit is configured to detect whether the main circuit module is faulty. The control circuit is configured to send a fault detection signal when the fault detecting unit detects a fault.

The fault detecting unit includes a phase loss detecting circuit and/or a bridge arm fault detecting circuit; the phase loss detecting circuit is electrically connected to a three-phase input of an AC power source passing through the fuse, and is configured to detect that the main circuit module is in the Whether the AC input terminal is faulty; the bridge arm fault detection circuit is electrically connected to the H inverter bridge, and is used to detect whether the H inverter bridge is faulty.

Wherein, the cascade type frequency converter further comprises a frequency converter control system, and when the fault detection unit detects that the main circuit module of the power unit is faulty, the control circuit generates a fault signal and sends the fault signal to the frequency converter control system, the frequency converter The control system sends a control signal to the power unit control module to trigger the bypass control circuit of the bypass module, and the bypass control circuit cuts the bypass circuit to bypass the faulty main circuit module.

Wherein, the cascade type frequency converter further comprises a frequency converter control system, and when the fault detection unit detects that the main circuit module of the power unit is faulty, the control circuit generates a fault signal and sends the fault signal to the frequency converter control system, the frequency converter The control system sends a control signal to trigger the bypass control circuit, and the bypass control circuit cuts the bypass circuit to bypass the faulty main circuit module.

The beneficial effects of the present invention are: a cascade type inverter, a power unit and a bypass module thereof according to the present invention, when the main circuit module fails and the bypass circuit is cut, a switching element of the bypass circuit And a diode is turned on to bypass the main circuit module of the corresponding power unit, while ensuring the normal operation of the frequency converter, the loss is small, the circuit structure is simple, and has a good cost advantage in the high-power inverter system.

In order to make the objects, technical solutions and advantages of the present invention more clear, a cascading type inverter, a power unit and a bypass module thereof according to the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the scope of the embodiments and the claims, the terms "a" and "the" may mean a single or plural.

As used herein, "about", "about" or "substantially" is used to modify any quantity that may vary somewhat, but such slight variations do not alter the nature. In the embodiments, the numerical values modified by "about", "about" or "substantially" are generally allowed to be within 20%, preferably within 10%, unless otherwise stated. More preferably, it is within five percent.

Embodiment 1

As shown in FIG. 2, a first embodiment of the present invention provides a cascaded frequency converter including a phase shifting transformer T11 and at least one power unit.

As shown in FIG. 2, as an example, is a schematic diagram of a 6 kV cascaded frequency converter system with 18 power units, the cascaded frequency converter including a phase shifting transformer T11 and 18 power units arranged in a three-phase cascade. (Power Cell), wherein each phase is cascaded by 6 power units, and the 6 low voltage power units output high voltage by cascading.

3 is a circuit diagram of a power unit having a bypass module 2 of FIG. 2, the power unit having the bypass module 2 including a main circuit module 1, a bypass module 2, and a power unit control module 3. As an implementation manner, the main circuit module 1 includes a fuse 11, a rectifier 12, a bus capacitor 13, and an H inverter bridge (inverter bridge arm) 14.

As an implementation manner, three-phase (U, V, W) outputs of one secondary winding of the phase shifting transformer are respectively connected to three-phase input terminals of one power unit, and the three-phase alternating current is rectified into direct current by the rectifier 12, In an embodiment, the rectifier 12 is diode rectified, and in other embodiments, may be other forms of rectifier. The DC voltage outputted by the rectifier 12 is connected to the bus capacitor 13, and then the H inverter bridge 14 inverts the DC voltage into an AC voltage. Each H inverter bridge 14 includes a first output terminal A and a second output terminal. B, that is, the main circuit module 1 of each power unit has a first output terminal A and a second output terminal B.

As shown in FIG. 2, in the cascaded frequency converter, the power unit A1, A2, A3, A4, A5, A6 cascades the first phase voltage of the output inverter, that is, the second output terminal B of the power unit A1 is connected to the power. The first output A of the unit A2, the second output B of the power unit A2 is connected to the first output A of the power unit A3, and the second output B of the power unit A3 is connected to an output A of the power unit A4, the power unit The second output terminal B of A4 is connected to the first output terminal A of the power unit A5, and the second output terminal B of the power unit A5 is connected to the first output terminal A of the power unit A6 to obtain the first phase output of the frequency converter. Similarly, the power units B1, B2, B3, B4, B5, B6 are cascaded to obtain the second phase output of the frequency converter, and the power units C1, C2, C3, C4, C5, C6 are cascaded to obtain the frequency conversion. The third phase output of the device, the output three-phase voltage is supplied to a three-phase load such as a motor.

The phase shifting transformer T11 in the first embodiment of the present invention is a prior art, and the phase shifting transformer T11 can be realized by those skilled in the art according to the technical solution disclosed in the first embodiment of the present invention. Therefore, in the first embodiment of the present invention, A detailed description will be given one by one.

As an implementation manner, the bypass module 2 of the first embodiment of the present invention includes a bypass circuit 21 and a bypass control circuit 22.

As an implementation, the H-inverter bridge 14 of the power unit can be constructed of any switching element whose switching state is controlled by its control terminal. As a possible implementation, the switching element of the H inverter bridge 14 of the power unit is an insulated gate bipolar transistor (IGBT), which includes a third insulated gate bipolar transistor Q3 and a fourth insulated gate double a pole transistor Q4, a fifth insulated gate bipolar transistor Q5 and a sixth insulated gate bipolar transistor Q6; a third insulated gate bipolar transistor Q3 and a fourth insulated gate bipolar transistor Q4 are connected in series to form the H inverter A bridge arm of the bridge 14, a fifth insulated gate bipolar transistor Q5 and a sixth insulated gate bipolar transistor Q6 are connected in series to form the other bridge arm of the H inverter bridge 14. Both ends of the two bridge arms are electrically connected to the H inverter bridge 14 constituting the power unit. The midpoint of one of the bridge arms of the H inverter bridge 14 is the first output end of the H inverter bridge 14 (ie, the main circuit module 1), that is, the output end A; the middle of the other bridge arm of the H inverter bridge 14 The point is the second output of the H inverter bridge 14 (ie, the main circuit module 1), that is, the output terminal B. And the two output ends of the main circuit module 1 are connected to the two input ends of the bypass circuit 21.

As shown in FIG. 4, as an embodiment, the power unit control module 3 includes a control circuit 31 and a fault detecting unit 32. The fault detection unit 32 includes a phase loss detection circuit 321 and/or a bridge arm fault detection circuit 322. In other embodiments, the power unit may also include other forms of fault detection circuitry.

When the power unit of the cascade type inverter is working normally, the bypass module 2 of the present invention does not work, and the output ends of the inverter bridge arms in the power units of the inverter phases are connected in series to obtain the output of each phase of the inverter. Once one or more of the power units in the cascaded frequency converter fails, the phase loss detection circuit 321 detects that there is a phase loss at the input of the power unit and/or the bridge arm fault detection circuit 322 detects the main circuit module 1 When the inverter bridge arm fails, the control circuit 31 generates a fault signal and sends it to the inverter control system (not shown); then the inverter control system sends a control signal to the power unit control module 3 to trigger the bypass module 2 Bypass control circuit 22, bypass control circuit 22 cuts the bypass circuit 21 to bypass the main circuit module of the corresponding power unit; or, the inverter control system (not shown) directly transmits the control signal to the bypass The control circuit 22, after which the bypass control circuit 22 cuts the bypass circuit 21 to bypass the main circuit module 1 of the corresponding failed power unit. In this way, even if one or more of the power units fail, the entire cascaded inverter can continue to work, greatly improving the reliability of the operation of the inverter system.

Embodiment 2

As a possible implementation, the power unit bypass module of the cascade type inverter of the first embodiment of the present invention includes a bypass circuit 21 and a bypass control circuit 22.

The bypass circuit 21 includes a first switching element, a second switching element, a first diode and a second diode;

The bypass circuit 21 includes a first input end and a second input end. The first input end is electrically connected to the first output end of the main circuit module 1 , the second input end and the main circuit module The second output of 1 is electrically connected. When the main circuit module 1 fails and the bypass circuit 21 is switched to work, a switching element of the bypass circuit 21 and a diode are turned on to bypass the main circuit module 1 of the corresponding power unit.

The first switching element and the second switching element are any switching elements whose switching states are controlled by their control terminals.

As shown in FIG. 5, as an implementation manner, the switching element of the bypass circuit 21 is an insulated gate bipolar transistor, and the bypass circuit 21 includes a first insulated gate bipolar transistor Q1 and a second insulated gate bipolar transistor. Q2, a first diode D1 and a second diode D2.

The first insulated gate bipolar transistor Q1 and the second insulated gate bipolar transistor Q2 are connected in series to form a first bridge arm, an emitter of the first insulated gate bipolar transistor Q1 and a second insulated gate bipolar transistor The collector of Q2 is electrically connected. The first diode D1 and the second diode D2 are connected in series to form a second bridge arm, and an anode of the first diode D1 and a cathode of the second diode D2 are electrically connected. The two ends of the first bridge arm and the second bridge are butted, that is, the collector of the first insulated gate bipolar transistor Q1 is electrically connected to the cathode of the first diode D1, and the second insulated gate bipolar transistor Q2 is The emitter is electrically connected to the anode of the second diode D2.

The first insulated gate bipolar transistor Q1 and the second insulated gate bipolar transistor Q2 are connected in series in the same direction, and the first diode D1 and the second diode D2 are also connected in series in the same direction.

A wire is drawn at a point between the first insulated gate bipolar transistor Q1 and the second insulated gate bipolar transistor Q2 as a first input terminal of the bypass circuit 21; at the first diode D1 and the second diode A point between the pole tubes D2 leads a wire as the second input of the bypass circuit 21.

As an implementation manner, as shown in FIG. 6, a schematic diagram of the main circuit module 1 and the bypass circuit 21 is connected. The first output terminal A of the main circuit module 1 of the power unit is electrically connected to the first input end of the bypass circuit 21; the second output terminal B of the main circuit module 1 of the power unit is electrically connected to the bypass circuit 21 The second input, that is, the point A shown in FIG. 3 is also the first input of the bypass circuit 21, and the point B is also the second input of the bypass circuit 21.

The first diode D1 of the bypass circuit 21 and the first insulated gate bipolar transistor Q1 form a branch; and the second diode D2 and the second insulated gate bipolar transistor Q2 form another branch. One of the two branches is turned on during the negative half cycle or the positive half cycle of the AC output.

As shown in FIG. 7, as the current received at the first input terminal (A) of the bypass circuit 21 is negative, the current received at the second input terminal (B) is positive, that is, the inverter arm of the power unit. When an output terminal A flows current and the second output terminal B of the inverter bridge arm of the power unit flows current, the main circuit module 1 fails and the bypass circuit 21 is cut, the first two poles of the bypass circuit 21 The tube D1 and the first insulated gate bipolar transistor Q1 are turned on to bypass the corresponding main circuit module 1, so that the entire cascade type inverter can continue to operate, and the current direction is as indicated by an arrow in FIG.

As shown in FIG. 8, as the current received at the first input (A) of the bypass circuit 21 is positive, the current received at the second input (B) is negative, that is, the first of the inverter arms of the power unit. When the output terminal A flows current and the second output terminal B of the inverter bridge arm of the power unit flows out of the current, the main circuit module 1 fails and the bypass circuit 21 cuts off, the second diode of the bypass circuit 21 D2 and the second insulated gate bipolar transistor Q2 are turned on to bypass the corresponding main circuit module 1, so that the entire cascade type inverter can continue to operate, and the current direction is as shown by the arrow in FIG.

As shown in FIG. 9, as another implementation manner of the bypass circuit 21, the collector of the first insulated gate bipolar transistor Q1 and the emitter of the second insulated gate bipolar transistor Q2 are electrically connected to each other. The first bridge arm of the circuit 21; the cathode of the first diode D1 and the anode of the second diode D2 are electrically connected to form a second bridge arm of the bypass circuit 21, the first bridge arm and the second bridge Both ends of the arm are electrically connected. The midpoint of the first bridge arm serves as the first input A of the bypass circuit 21; the midpoint of the second bridge serves as the second input B of the bypass circuit 21.

If the current received at the first input terminal (A) of the bypass circuit 21 is positive, and the current received at the second input terminal (B) is negative, that is, the first output terminal A of the inverter bridge arm of the power unit flows current, When the second output terminal B of the inverter bridge arm of the power unit is out of current, the main circuit module 1 fails and the bypass circuit 21 is cut, the first diode D1 of the bypass circuit 21 and the first insulated gate The bipolar transistor Q1 is turned on to bypass the corresponding main circuit module 1, so that the entire cascaded inverter can continue to operate.

If the current received at the first input terminal (A) of the bypass circuit 21 is negative, the current received by the second input terminal (B) is positive, that is, the first output terminal A of the inverter bridge arm of the power unit flows current, When the second output terminal B of the inverter arm of the power unit flows current, the main circuit module 1 fails and the bypass circuit 21 is cut, the second diode D2 and the second insulated gate of the bypass circuit 21 The bipolar transistor Q2 is turned on to bypass the corresponding main circuit module 1, so that the entire cascaded inverter can continue to operate.

As shown in FIG. 10, as another implementation manner of the bypass circuit 21, the emitter of the first insulated gate bipolar transistor Q1 and the anode of the first diode D1 are electrically connected to form a bypass circuit 21. The first bridge arm, the emitter of the second insulated gate bipolar transistor Q2 and the anode of the second diode D2 are electrically connected to form the second bridge arm of the bypass circuit 21, the first bridge arm and the second bridge Both ends of the arm are electrically connected. The midpoint of the first bridge arm serves as the first input A of the bypass circuit 21; the midpoint of the second bridge serves as the second input B of the bypass circuit 21.

If the current received at the first input terminal (A) of the bypass circuit 21 is positive, and the current received at the second input terminal (B) is negative, that is, the first output terminal A of the inverter bridge arm of the power unit flows current, When the second output terminal B of the inverter arm of the power unit flows out of current, the main circuit module 1 fails and the bypass circuit 21 is cut, the first diode D1 and the second insulated gate of the bypass circuit 21 The bipolar transistor Q2 is turned on to bypass the corresponding main circuit module 1, so that the entire cascaded inverter can continue to operate.

If the current received at the first input terminal (A) of the bypass circuit 21 is negative, the current received by the second input terminal (B) is positive, that is, the first output terminal A of the inverter bridge arm of the power unit flows current, When the second output terminal B of the inverter arm of the power unit flows current, the main circuit module 1 fails and the bypass circuit 21 is cut, the second diode D2 of the bypass circuit 21 and the first insulated gate The bipolar transistor Q1 is turned on to bypass the corresponding main circuit module 1, so that the entire cascaded inverter can continue to operate.

As shown in FIG. 11, the power unit bypass module of the cascade type inverter is further provided with a bypass control circuit 22, and the bypass control circuit 22 is electrically connected to the switching element of the bypass circuit 21 for controlling The switching element is turned off or on.

The connection relationship between the bypass control circuit 22 and the bypass circuit 21 will be described by taking the bypass circuit 21 shown in FIG. 5 as an example. The gates of the first insulated gate bipolar transistor Q1 and the second insulated gate bipolar transistor Q2 are connected to the bypass control circuit 22, and the bypass control circuit 22 is configured to control the two insulated gate bipolar transistors The bypass control circuit 22 is also connected to the power unit control module.

When the power unit of the cascade type inverter works normally, the bypass module 2 of the present invention does not work, and the output ends of the inverter bridge arms in the power units of the inverter phases are connected in series to obtain the phases of the inverter bridge arm. Output. Once one or more power units in the cascaded frequency converter fail, the control circuit sends a fault signal detected by the fault detection circuit to the frequency converter control system (not shown); and then the control signal is sent by the frequency converter control system. Go to the power unit control module 3, trigger the bypass control circuit 22 of the power unit, and the bypass control circuit 22 cuts the bypass circuit 21 to short-circuit the main circuit module 1 of the failed power unit, thereby Ensure that when the main circuit module 1 of a power unit fails, switch to the bypass of the power unit to work, and thus does not affect the normal operation of the other power units of the entire cascade inverter, greatly improving the operation of the inverter system. Reliability.

Embodiment 3

As an implementation manner, the bypass module 2 provided by the present invention includes a bypass circuit 21 and a bypass control circuit 22, and the bypass circuit 21 includes a first insulated gate bipolar transistor Q1 and a second insulated gate bipolar. The transistor Q2, the first diode D1, the second diode D2, and an absorption circuit 211.

As an implementation manner, the absorbing circuit 211 is a snubber capacitor C1. As shown in FIG. 12, taking the bypass circuit 21 shown in FIG. 5 as an example, the snubber capacitor C1 is connected in parallel to the bypass circuit 21, that is, the first diode D1 and the second diode D2 are connected in series. Both ends of the bridge arm.

Referring to FIG. 13, FIG. 13 shows an embodiment in which the bypass circuit 21 shown in FIG. 12 is connected to the main circuit module 1. The two output ends of the main circuit module 1 and the bypass circuit 21 are respectively The two inputs are electrically connected.

As an implementation manner, the power unit further includes a first protection resistor R1 and a second protection resistor R2. One end of the first protection resistor R1 is connected to one end of the absorption capacitor C1, and the other end of the first protection resistor R1 is One end of the bus capacitor 13 of the main circuit module 1 is connected; one end of the second protection resistor R2 is connected to the other end of the absorption capacitor C1, and the other end of the second protection resistor R2 is connected to the bus of the main circuit module 1 The other end of the capacitor 13 is connected.

The leakage inductance of the bus capacitor 13 of the main circuit module 1 is relatively large and/or when the main circuit module 1 fails, causing the insulated gate bipolar transistor of the H inverter bridge 14 of the main circuit module 1 to be turned off quickly, if When the output of the main circuit module 1 is short-circuited, it is possible to generate a high voltage spike between the output terminals A and B of the main circuit module 1 when the H-inverter bridge 14 of the main circuit module 1 is protected from being turned off. / or with high-frequency voltage oscillation, and the oscillation peak is large. This voltage spike may approach or exceed the voltage safe operating region of a device such as an insulated gate bipolar transistor of the bypass circuit 21.

Therefore, in order to prevent the device such as the insulated gate bipolar transistor from being damaged, as an implementation manner, the bypass circuit 21 is provided with the absorption capacitor C1, and the first protection resistor R1 and the second protection resistor R2 are disposed. When the power unit is working normally, the main circuit module 1 charges the absorption capacitor C1 through the first protection resistor R1 and the second protection resistor R2 to prevent the bypass circuit 21 from forming a full bridge rectification structure when the power unit is working normally. Capacitor C1 is charged to cause abnormal operation of the power unit, which improves the reliability of the system operation. Since the leakage currents of the insulated gate bipolar transistors Q1 and Q2 and the diodes D1 and D2 are small, the losses of the first protection resistor R1 and the second protection resistor R2 are also relatively small.

As shown in FIG. 14, as an embodiment, the absorbing circuit 211 further includes a third resistor R3. The snubber capacitor C1 and the third resistor R3 are connected in series and then connected in parallel to the bypass circuit 21, that is, both ends of the bridge arm composed of the first diode D1 and the second diode D2 connected in series.

As shown in FIG. 15, the bypass circuit 21 further includes a series RC branch and a bypass circuit state detecting unit 212, wherein the RC branch routes the fourth resistor R4 and the storage capacitor C2 are connected in series. The configuration is paralleled at both ends of the bridge arm of the bypass circuit 21, and the bypass circuit state detecting unit 212 is configured to detect whether the bypass circuit 21 is cut or not.

When the power unit is working normally, the output terminal (A, B) outputs a pulse voltage, and the anti-parallel diode inherent in the first insulated gate bipolar transistor Q1 or the second insulated gate bipolar transistor Q2 of the bypass circuit 21 is passed. And the second diode D2 or the first diode D1 of the bypass circuit 21 forms a rectifying circuit for charging the storage capacitor C2 of the parallel RC branch, and the resistance of the fourth resistor R4 can be selected greatly. For example, for several tens of kiloohms, the voltage of the storage capacitor C2 is always kept at a high voltage.

When the main circuit module 1 of the power unit fails, the bypass circuit 21 is switched to work, that is, the insulated gate bipolar transistors Q1 and Q2 are turned on at the same time, so that the voltage on the capacitor C2 of the RC branch is quickly placed to zero. . Therefore, the operating state of the bypass circuit 21 can be determined by detecting the voltage on the capacitor C2 of the RC branch. When the voltage on the capacitor C2 is high, the power unit is considered to be working normally, that is, the bypass circuit 21 is not cut. When the voltage on the capacitor C2 is low, it is considered that the main circuit module 1 of the power unit is malfunctioning, that is, the bypass circuit 21 is cut to work.

As an implementation manner, when the power level of the inverter is relatively large, the first switching element and the second switching element of the bypass circuit 21 in the second embodiment and the third embodiment of the present invention may be configured to be connected in parallel by multiple switching elements. Composition. For example, when the first switching element and the second switching element are a first insulated gate bipolar transistor and a second insulated gate bipolar transistor, the first insulated gate bipolar transistor and the second insulated gate bipolar The transistor can be constructed in parallel with a plurality of insulated gate bipolar transistors.

In the bypass circuit 21 of the power unit of the cascade type inverter of the embodiment of the present invention, when the bypass circuit 21 is cut, only one branch is working, that is, only one branch of the diode and the switching element at each moment. The power devices are turned on, the number of devices to be turned on is small, and the loss is relatively small, and the bypass circuit 21 provided by the present invention has a relatively simple structure and high reliability. Moreover, the reliability of the bypass circuit 21 can be further protected by the absorption capacitor C1 and the protection resistors (R1, R2), thereby improving the reliability of the cascade type inverter. Moreover, the operating state of the bypass circuit 21 can be accurately detected by an RC branch and a bypass circuit state detecting unit 212.

It should be understood that various modifications and changes may be made thereto without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the invention,

1. . . Main circuit module

11. . . Fuse

12. . . Rectifier

13. . . Bus capacitance

14. . . H inverter bridge (inverter bridge arm)

2. . . Bypass module

twenty one. . . Bypass circuit

211. . . Absorption circuit

212. . . Bypass circuit state detection unit

twenty two. . . Bypass control circuit

3. . . Power unit control module

31. . . Control circuit

32. . . Fault detection unit

321. . . Phase loss detection circuit

322. . . Bridge arm fault detection circuit

K _M . . . Auxiliary switch

T11. . . Phase shifting transformer

A. . . First output

A1~A6. . . Power unit

B. . . Second output

B1~B6. . . Power unit

C1~C6. . . Power unit

C1. . . Absorption capacitor

C2. . . Storage capacitor

D1. . . First diode

D2. . . Second diode

Q1. . . First insulated gate bipolar transistor

Q2. . . Second insulated gate bipolar transistor

Q3. . . Third insulated gate bipolar transistor

Q4. . . Fourth insulated gate bipolar transistor

Q5. . . Fifth insulated gate bipolar transistor

Q6. . . Sixth insulated gate bipolar transistor

R1. . . First protection resistor

R2. . . Second protection resistor

R3. . . Third resistance

R4. . . Fourth resistor

1 is a schematic diagram of a prior art contactor bypass circuit.

2 is a schematic structural view of a cascade type inverter of the present invention.

3 is a schematic diagram of an embodiment of a power unit of the present invention.

4 is a schematic diagram of another embodiment of a real power unit of the present invention.

FIG. 5 is a schematic structural view of an embodiment of a bypass circuit according to the present invention.

FIG. 6 is a schematic diagram of a main circuit module and a bypass circuit connected according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of current flow direction of the bypass circuit of the present invention.

FIG. 8 is a schematic diagram of another current flow direction of the bypass circuit of the present invention.

FIG. 9 is a schematic structural view of another embodiment of a bypass circuit according to the present invention.

FIG. 10 is a schematic structural view of still another embodiment of a bypass circuit according to the present invention.

11 is a schematic structural view of an embodiment of a bypass module of the present invention.

FIG. 12 is a schematic structural view of a bypass circuit with an absorbing capacitor according to the present invention.

FIG. 13 is a schematic diagram of a connection between a main circuit module and a bypass circuit according to another embodiment of the present invention.

FIG. 14 is a schematic structural view of a bypass circuit with a snubber capacitor and a third resistor according to the present invention.

FIG. 15 is a schematic diagram showing a connection between a main circuit module and a bypass circuit according to still another embodiment of the present invention.

1. . . Main circuit module

twenty one. . . Bypass circuit

A. . . First output

B. . . Second output

D1. . . First diode

D2. . . Second diode

Q1. . . First insulated gate bipolar transistor

Q2. . . Second insulated gate bipolar transistor

Q3. . . Third insulated gate bipolar transistor

Q4. . . Fourth insulated gate bipolar transistor

Q5. . . Fifth insulated gate bipolar transistor

Q6. . . Sixth insulated gate bipolar transistor

Claims (27)

A cascaded inverter power unit bypass module for bypassing a main circuit module of the power unit, the main circuit module comprising a fuse, a rectifier, a bus capacitor, and an H inverter bridge, from the H inverter Two points are drawn on the bridge as a first output end and a second output end of the main circuit module, and are characterized by comprising a bypass circuit;
The bypass circuit includes a first switching element, a second switching element, a first diode and a second diode;
The bypass circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a switching element, and the second bridge arm includes a diode;
Leading a point from the first bridge arm of the bypass circuit as a first input end of the bypass circuit, and extracting a point from the second bridge arm of the bypass circuit as a second input end of the bypass circuit, the first An input terminal is electrically connected to the first output end of the main circuit module, and the second input end is electrically connected to the second output end of the main circuit module;
When the main circuit module fails and the bypass circuit is cut, the switching element of the bypass circuit and a diode are turned on to bypass the main circuit module of the corresponding power unit. The cascading type inverter power unit bypass module according to claim 1, wherein the first switching element is a first insulated gate bipolar transistor, and the second switching element is a second insulation Gate bipolar transistor. The cascading type inverter power unit bypass module according to claim 2, wherein the bypass circuit comprises the first insulated gate bipolar transistor and the second insulated gate bipolar transistor The first diode and the second diode;
The emitter of the first insulated gate bipolar transistor is electrically connected to the collector of the second insulated gate bipolar transistor, and the anode of the first diode and the cathode of the second diode are electrically connected. The collector of the first insulated gate bipolar transistor is electrically connected to the cathode of the first diode, and the emitter of the second insulated gate bipolar transistor is electrically connected to the anode of the second diode;
A wire is drawn at a point between the first insulated gate bipolar transistor and the second insulated gate bipolar transistor as a first input end of the bypass circuit;
A wire is drawn at a point between the first diode and the second diode as a second input of the bypass circuit;
The first diode and the first insulated gate bipolar transistor form a first branch, and the second diode and the second insulated gate bipolar transistor form a second branch;
The first output end of the main circuit module is electrically connected to the first input end of the bypass circuit, and the second output end of the main circuit module is electrically connected to the second input end of the bypass circuit. The cascading type inverter power unit bypass module according to claim 3, wherein the current input by the first input end of the bypass circuit is negative, and the current received by the second input terminal is positive. When the main circuit module of the power unit fails and the bypass circuit is cut, the first diode of the bypass circuit and the first insulated gate bipolar transistor are turned on to bypass the main circuit of the corresponding power unit. The module allows the entire cascaded inverter to continue to operate. The cascading type inverter power unit bypass module according to claim 3, wherein the current input by the first input terminal of the bypass circuit is positive, and the current received by the second input terminal is negative. When the main circuit module of the power unit fails and the bypass circuit is cut, the second diode of the bypass circuit and the second insulated gate bipolar transistor are turned on to bypass the main circuit of the corresponding power unit. The module allows the entire cascaded inverter to continue to operate. The cascading type inverter power unit bypass module according to claim 2, wherein the bypass circuit comprises the first insulated gate bipolar transistor and the second insulated gate bipolar transistor The first diode and the second diode;
The collector of the first insulated gate bipolar transistor is electrically connected to the emitter of the second insulated gate bipolar transistor, and the cathode of the first diode is electrically connected to the anode of the second diode. An emitter of the first insulated gate bipolar transistor is electrically connected to an anode of the first diode, and a collector of the second insulated gate bipolar transistor is electrically connected to a cathode of the second diode;
A wire is drawn at a point between the first insulated gate bipolar transistor and the second insulated gate bipolar transistor as a first input end of the bypass circuit;
A wire is drawn at a point between the first diode and the second diode as a second input of the bypass circuit;
The first diode and the first insulated gate bipolar transistor form a first branch, and the second diode and the second insulated gate bipolar transistor form a second branch;
The first output end of the main circuit module is electrically connected to the first input end of the bypass circuit, and the second output end of the main circuit module is electrically connected to the second input end of the bypass circuit. The cascading type inverter power unit bypass module according to claim 6 is characterized in that the current received by the first input end of the bypass circuit is positive, and the current received by the second input terminal is negative. When the main circuit module of the power unit fails and the bypass circuit is cut, the first diode of the bypass circuit and the first insulated gate bipolar transistor are turned on to bypass the main circuit of the corresponding power unit. The module allows the entire cascaded drive to continue to operate. The cascading type inverter power unit bypass module according to claim 6 is characterized in that the current received by the first input end of the bypass circuit is negative, and the current received by the second input terminal is positive. When the main circuit module of the power unit fails and the bypass circuit is cut, the second diode of the bypass circuit and the second insulated gate bipolar transistor are turned on to bypass the main circuit of the corresponding power unit. The module allows the entire cascaded drive to continue to operate. The cascading type inverter power unit bypass module according to claim 2, wherein the bypass circuit comprises the first insulated gate bipolar transistor and the second insulated gate bipolar transistor The first diode and the second diode;
The emitter of the first insulated gate bipolar transistor is electrically connected to the anode of the first diode, and the emitter of the second insulated gate bipolar transistor is electrically connected to the anode of the second diode. The collector of the first insulated gate bipolar transistor is electrically connected to the cathode of the second diode, and the collector of the second insulated gate bipolar transistor is electrically connected to the cathode of the first diode;
A wire is drawn at a point between the first insulated gate bipolar transistor and the first diode as a first input end of the bypass circuit;
A wire is drawn at a point between the second insulated gate bipolar transistor and the second diode as a second input end of the bypass circuit;
The first diode and the second insulated gate bipolar transistor form a first branch, and the second diode and the first insulated gate bipolar transistor form a second branch;
The first output end of the main circuit module is electrically connected to the first input end of the bypass circuit, and the second output end of the main circuit module is electrically connected to the second input end of the bypass circuit. The cascading type inverter power unit bypass module according to claim 9 is characterized in that the current received by the first input end of the bypass circuit is positive, and the current received by the second input terminal is negative. When the main circuit module of the power unit fails and the bypass circuit is cut, the first diode and the second insulated gate bipolar transistor of the bypass circuit are turned on to bypass the main circuit of the corresponding power unit. The module allows the entire cascaded drive to continue to operate. The cascading type inverter power unit bypass module according to claim 9 is characterized in that the current received by the first input end of the bypass circuit is negative, and the current received by the second input terminal is positive. When the main circuit module of the power unit fails and the bypass circuit is cut, the second diode of the bypass circuit and the first insulated gate bipolar transistor are turned on to bypass the main circuit of the corresponding power unit. The module allows the entire cascaded drive to continue to operate. The cascading type inverter power unit bypass module according to claim 1, wherein the bypass circuit further comprises an absorbing circuit, wherein the absorbing circuit comprises an absorbing capacitor, and the absorbing capacitor is connected in parallel Both ends of the circuit. The cascading type inverter power unit bypass module according to claim 12, wherein the absorbing circuit further comprises a third protection resistor;
The absorbing capacitor and the third protection resistor are connected in series and are connected in parallel to both ends of the bypass circuit. The cascading type inverter power unit bypass module according to claim 12, further comprising a first protection resistor and a second protection resistor;
One end of the first protection resistor is electrically connected to one end of the absorption capacitor, and the other end of the first protection resistor is electrically connected to one end of the bus capacitor; and one end of the second protection resistor is electrically connected to the other end of the absorption capacitor. The other end of the second protection resistor is electrically connected to the other end of the bus capacitor. The cascading type inverter power unit bypass module according to claim 1, wherein the bypass circuit further comprises an RC branch and a bypass circuit state detecting unit;
The RC branch includes a fourth resistor and a storage capacitor, and the fourth resistor and the storage capacitor are connected in series and connected in parallel at both ends of the bypass circuit;
The bypass circuit state detecting unit is connected in parallel with the RC branch to detect whether the bypass circuit operates. The cascading type inverter power unit bypass module according to claim 1, further comprising a bypass control circuit, the bypass control circuit and the first switching element and the second switch And a connection for controlling conduction or disconnection of the first switching element and the second switching element. The cascading type inverter power unit bypass module according to claim 2, wherein the first insulated gate bipolar transistor and the second insulated gate bipolar transistor are gated The pole is connected to the bypass control circuit. A cascade type inverter power unit, comprising: a main circuit module, a power unit control module and a bypass module;
The main circuit module comprises a fuse, a rectifier, a bus capacitor, and an H inverter bridge, and two points are drawn from the H inverter bridge as two output ends of the main circuit module;
The bypass module is the bypass module according to any one of claims 1 to 17;
The two input ends of the bypass circuit are connected to the two output ends of the main circuit module;
The power unit control module is electrically connected to the main circuit module and the bypass module. The cascading type inverter power unit according to claim 18, wherein the power unit control module comprises a control circuit and a fault detecting unit;
The fault detecting unit is configured to detect whether the main circuit module is faulty;
The control circuit is configured to send a fault detection signal when the fault detecting unit detects a fault. The cascading type inverter power unit according to claim 19, wherein the fault detecting unit comprises a phase loss detecting circuit and/or a bridge arm fault detecting circuit;
The phase loss detecting circuit is electrically connected to the three-phase input of the AC power source passing through the fuse, and is configured to detect whether the main circuit module is faulty at the AC input end;
The bridge arm fault detecting circuit is electrically connected to the H inverter bridge, and is configured to detect whether the H inverter bridge is faulty. A cascade type frequency converter comprising a phase shifting transformer, a power unit and a three-phase load, wherein the power unit comprises a main circuit module, a bypass module and a power unit control module;
The main circuit module comprises a fuse, a rectifier, a bus capacitor, and an H inverter bridge, and two points are drawn from the H inverter bridge as two output ends of the main circuit module;
The bypass module is the bypass module according to any one of claims 1 to 17;
The two input ends of the bypass circuit are connected to the two output ends of the main circuit module;
The power unit control module is electrically connected to the main circuit module and the bypass module. The cascade type inverter of claim 21, wherein the phase shifting transformer comprises at least one secondary winding. The cascade type inverter of claim 22, wherein the three-phase output of each secondary winding of the phase shifting transformer is respectively connected to the three-phase input of the power unit. The cascading type inverter of claim 21, wherein the power unit control module comprises a control circuit and a fault detecting unit;
The fault detecting unit is configured to detect whether the main circuit module is faulty;
The control circuit is configured to send a fault detection signal when the fault detecting unit detects a fault. The cascading type inverter of claim 24, wherein the fault detecting unit comprises a phase loss detecting circuit and/or a bridge arm fault detecting circuit;
The phase loss detecting circuit is electrically connected to the three-phase input of the AC power source passing through the fuse, and is configured to detect whether the main circuit module is faulty at the AC input end;
The bridge arm fault detecting circuit is electrically connected to the H inverter bridge, and is configured to detect whether the H inverter bridge is faulty. The cascading type inverter of claim 21, wherein the cascade type inverter further comprises a frequency converter control system, and when the fault detecting unit detects that the main circuit module of the power unit is faulty The control circuit generates a fault signal to be sent to the inverter control system, and the inverter control system sends a control signal to the power unit control module to trigger the bypass control circuit of the bypass module, and the bypass control circuit The bypass circuit is cut to work to bypass the failed main circuit module. The cascading type inverter of claim 21, wherein the cascade type inverter further comprises a frequency converter control system, and when the fault detecting unit detects that the main circuit module of the power unit is faulty The control circuit generates a fault signal sent to the inverter control system, and the inverter control system sends a control signal to trigger the bypass control circuit, and the bypass control circuit cuts the bypass circuit to bypass the faulty main circuit. Module.